<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>05流程控制</title>
</head>
<body>
<script>
  //1.顺序结构
  console.log(1);
  console.log(2);
  console.log(3);
  //2.分支结构
  let username = 'rose';
  if(!username){//若用户名为空字符串,转为布尔是false,!false为true,走分支1
    alert('用户名不能为空!');
  }else{
    alert('欢迎'+username+'回归!');
  }
  //3.选择分支
  let gender = 10;
  switch (gender){
    case 1:
      console.log('男');
      break;
    case 0:
      console.log('女');
      break;
    default:
      console.log('未知');
  }

  //4.循环结构
  let names = ['张三','李四','王五'];
  for (let i = 0; i < names.length; i++){
    console.log(names[i]);
  }
  //如果用var定义变量,则i在循环结束后,仍然存在
  //console.log(i);

  //增强for循环 names表示当前要遍历的数组
  //let n表示当前遍历到的元素
  for (let n of names){
    console.log(n);
  }
</script>
</body>
</html>